Putting surfaces on typical putting greens are not totally smooth and have a variety of imperfections across the surface. Even on finely manicured, more perfect golf greens, when a golf ball comes to rest on the putting surface of a green, just the weight of the ball may cause a slight depression in the green's surface directly under the ball as the golfer walks from the place where the shot to the green was hit to the location on the green where the ball is at rest. Typically most conventional golf putters incorporate a smooth, flat ball-striking face with four to six degrees of loft, it being common wisdom this amount of loft is necessary to cleanly launch a golf ball sitting on the irregular surface. These putters provide a maximum surface area across the face to contact a golf ball. When a golf ball resting on an irregular surface of a green or in a shallow depression caused by the weight of the golf ball is struck with the smooth face type putter described above, the ball travels forward and slightly upward from the surface with a slight backward rotation. As the ball continues on its path to the target it bounces and skids before fully engaging the green's surface. Friction with the putting surface eventually causes the ball to assume a forward roll toward the target.
The undesirable skipping and skidding motion of the ball after the initial strike led to the development of putters with closely spaced grooves on the ball striking face to create lift with only one to two degrees of loft. The gripping effect of the face grooves combined with low loft enables the golf ball to be lifted off the green's surface causing the golf ball to roll almost immediately virtually eliminating the skipping and skidding described above.
Examples of grooved face putters include Applicant's own patents, U.S. Pat. No. 5,618,239, titled Groove Configuration for a Golf Club and U.S. Pat. No. 5,709,616, titled Groove Configuration for a Putter Type Golf Club Head. Both the patents teach the use of closely spaced, straight, horizontal grooves each with a slightly different groove configuration that grips and lifts a golf ball at impact by the putter face. U.S. Pat. No. 5,618,239 teaches the use of asymmetrical saw-toothed shaped grooves. U.S. Pat. No. 5,709,616 teaches the use of symmetrical grooves wherein the land area between the grooves is smaller than the groove spacing. In both of these patents, the reduced land area between the grooves provides a lesser contact surface presented to the golf ball, resulting in a softer hit than a smooth face putter. The groove structure of the grooved putters also allows the striking face to press into or dwell on the surface of the ball fractionally longer. While this increased dwell time produces a more immediate and accurate roll, it also softens the strike thus reducing the distance the ball will travel after impact.
Other attempts at providing a ball striking face configuration for more accurate golf ball roll is shown in U.S. Pat. No. 5,637,044 to Swash that uses a plurality of equally spaced concentric, arcuate grooves surrounding the center of percussion of the ball striking face of the putter. The arcuate configuration promotes the possibility of the ball going further off line when the ball is struck off center on a downward portion of the arcuate groove pattern or when a golfer swings the putter head in a diagonal stroke path creating side spin.
In addition, a wide variety of lines, geometrical designs and decorative patterns on the face of a putter have been used in an attempt to improve the contact between the putter face and the golf ball at impact during the execution of a putting stroke. All of these attempts have a consistent pattern across the putter face. For example, U.S. Pat. No. 6,224,497 to Antonious shows a golf putter with vertical grooves including a disclosed embodiment having grooves of a different vertical width.
U.S. Pat. No. 8,066,586 to Solheim et al teaches the use of grooves having a variable width and corresponding land areas on an iron type golf club, as seen with reference to FIG. 1, to control the way a golf ball reacts when struck with the club. The grooves are wider at the midpoint and are progressively narrower toward the heel and toe of the clubface. There are at least seven different groove configurations with variations of this groove structure. It is seen that the grooves are significantly spaced from each other on the striking face whereby the land areas between the grooves are at least two to three times wider than the width of the adjacent grooves no matter what shape the groove assumes. This spacing is required in order to conform to the requirements of the USGA, the governing body for golf. The spacing between the grooves disclosed in this patent limits or increases the degree of backspin caused by the high speed of an iron type club impacting a golf ball and would have little effect, if any, should the spacing be used with a putter where the impact speed is significantly less.